An inverter device controls an elevating speed of an elevator, a crane, a multistory parking lot, and a printing machine by adjusting a voltage and a frequency.
Patent Literature 1 discloses an inverter device that suppresses an over-torque state of an induction motor for winding up or rewinding a cable of a winch. When a torque current detected by a torque-current detecting circuit exceeds a set level and the induction motor becomes in the over-torque state, the inverter device described in Patent Literature 1 determines a frequency and a voltage of an AC voltage to be generated by an inverter based on a speed of the induction motor output from a speed detector.